The present invention relates to a push-button switch adapted to shift from a first OFF state to an ON state according to the increase of the amount of depression of a push button and then to shift to a second OFF state according to further depression of the push button, and also relates to a teaching pendant comprising the same.
In cases where, for example, a manual operation is performed on numerically controlled machines such as robots, an operator often enters a dangerous area to carry out his job. In such cases, a teaching pendant with a push-button switch, such as called an enable switch (or deadman switch), is used for preventing an accident due to contact with the machine during the work.
As shown in FIG. 34, a teaching pendant 600 is a portable unit which is used as connected with a control unit to teach a program to the robot or to operate the robot. The teaching pendant 600 includes an input keyboard 601 disposed on a main surface and a push-button switch (enable switch) 602 disposed on one side surface thereof. In some cases, the push-button switch 602 may be disposed on a rear surface of the teaching pendant 600. The teaching pendant 600 further includes a signal cable 603 for connection with the control unit not shown.
Such a teaching pendant employs a push-button switch which is called a snap action type, as shown in FIG. 35 for example.
As seen in FIG. 35, the push-button switch 602 includes a push button 605 and a microswitch 606 in opposing relation with the push button. The push button 605 is provided with a leaf spring 607 extended downwardly from a bottom surface thereof. Disposed on a top surface of the microswitch 606 are a resilient push plate 608 and an actuator 609. A bent portion 607a is formed at a tip of the leaf spring 607.
The push-button switch 602 is used as follows. First, the teaching pendant 600 incorporating the push-button switch 602 is connected, via the signal cable 603, with a control panel of a machine to be manually operated. If the push-button switch 602 is in the OFF state at this time, manipulating the keyboard 601 of the teaching pendant 600 does not effect the key entry.
Next, depressing the push button 605 brings the bent portion 607a of the leaf spring 607, moved in unison with the push button 605, into engagement with the push plate 608 of the microswitch 606. At the same time, the push plate 608 is resiliently deformed downward to press down the actuator 609, as shown in FIG. 36. This causes the actuator 609 to descend to bring a contact within the microswitch 606 into a contacted state, so that the microswitch 606 is shifted to the ON state.
The operator performs key entry via the keyboard 601 of the teaching pendant 600 while keeping the push button 605 depressed so as to maintain the microswitch in the ON state. If, during the operation, the operator releases the push button 605 sensing the danger of contacting some moving part of the machine manually operated, the push button 605 returns to the state shown in FIG. 35, thereby shifting the microswitch 606 to the first OFF state or the initial state. That is, the machine is brought into standstill.
In a case where the operator, who is in panic facing the imminent danger, further depresses the push button 605, the bent portion 607a of the leaf spring 607 slides on the push plate 608 to disengage therefrom, as shown in FIG. 37, so that the push plate 608 is returned to its original position by its restoring force. This shifts the microswitch 606 to the second OFF state for deactivating the machine.
Thus, the push-button switch 602 is adapted to permit the key entry through the keyboard 601 of the teaching pendant 600 only when the microswitch 606 is in the ON state. Furthermore, the push-button switch 602 can be set to any of the three positions (the first OFF state, ON state and second OFF state) according to the amount of depression of the push button 605. Therefore, the operator""s intent during the manual operation of the machine can be distinctly implemented and hence, the operator""s safety is ensured.
As the push-button switch having such three positions, there may be employed a push-button switch of a so-called slow action type, as shown in FIG. 38.
As shown in FIG. 38, such a push-button switch 701 includes a switch case 702, a push button 703 depressibly supported by the switch case 702, a pair of stationary terminals 705 each attached to a leaf spring 704 disposed within the switch case 703, a pair of movable terminals 707 attached to a bracket 706 and adapted to be brought into or out of contact with the stationary terminals 705, and a switching mechanism 708 moving in response to the depression of the push button 703 for bringing the movable terminals 707 into contact with the stationary terminals 705 and designed to separate the movable terminals 707 from the stationary terminals 705 when the depression of the push button reaches a predetermined amount. In the push-button switch 701, the movable terminal 707 and the stationary terminal 705 constitute a normally open contact.
The push button 703 is formed with an accommodating portion 709 defining a rectangular internal space in plan, the accommodating portion 709 formed with slopes 710 on opposite walls thereof.
The switching mechanism 708 includes an insertion member 712 disposed in the accommodating portion 709 of the push button 703 and formed with a pair of bores 711, a pair of slide blocks 713 disposed in the respective bores 711 of the insertion member 712 as allowed to move horizontally (the transverse direction as seen in FIG. 38), a helical spring 714 interconnecting the insertion member 712 and the bracket 706 and urging the movable terminals 707 downwardly, and a shaft member 715 projecting downward from the bracket 706.
The slide blocks 713 are urged toward opposite ends of the push button 703 by helical springs 716 disposed in the respective bores 711 of the insertion member 712. The slide blocks 713 are each formed with a slope 717 at one end thereof for engagement with each of the slopes 710 of the push button 703.
The shaft member 715 has its lower portion inserted in a bore 718 formed at a bottom of the switch case 702. Disposed in the bore 718 is a return spring 719, an upper end of which is fixed to a lower end of the shaft member 715. Thus, the shaft member 715 is normally urged upward by an urging force of the return spring 719.
When the undepressed push button 703 in the first OFF state is depressed, the switching mechanism 708 is moved downward as interlocked with the push button 703 thereby pushing down the movable terminals 707 into contact with the stationary terminals 705, as shown in FIG. 39. Thus, the push-button switch 701 is shifted to the ON state. At this time, the slopes 710 of the push button 703 apply a pressure to the slopes 717 of the slide blocks 713 for moving the slide blocks 713 inwardly. However, the urging force of the helical spring 714 urging the slide blocks 713 upwardly is greater than this pressure, so that the slide blocks 713 stay at places to maintain the engagement with the push button 703.
When the push button 703 in the ON state is further depressed, the urging force of the helical spring 714 surpasses the force for urging the slide blocks 713 outwardly, so that the slide blocks 713 are moved inwardly of the insertion member 712 as the slopes 717 of the slide blocks 713 slid on the slopes 710 of the push button 703, as shown in FIG. 40. This results in the disengagement of the slide blocks 713 from the push button 703, while the switching mechanism 708 is moved upward by the return spring 719, as shown in FIG. 41. This movement involves an upward movement of the movable terminals 707, which are separated from the stationary terminals 705. Thus, the push-button switch 701 is shifted to the second OFF state.
The above conventional push-button switches 602, 701 are provided with only one contact. In a case where the contact does not work due to failure or the like during the data input operation, for example, the push-button switch is unable to respond to the ON/OFF switching, thus losing the function as the enable switch. Accordingly, the push-button switch fails to assure reliability.
In the push-button switch 701 of slow action type, the amount of depression of the push button 703 to shift the switch from the first OFF state to the ON state is equal to the amount of depression of the push button 703 to shift the switch from the ON state to the first OFF state. Therefore, if the depressed push button 703 of the push-button switch 701 in the ON state is released a little, for example, the movable terminals 707 move away from the stationary terminals 705. That is, the push-button switch 701 is prone to return from the ON state to the first OFF state. In the case of a long data input operation through the teaching pendant, for example, the operator may encounter an inadvertent interruption of the data input because an unintentional slight easing of the depression of the push button will return the push-button switch 701 to the first OFF state.
Furthermore, the push-button switch 701 of slow action type does not provide a tactile click-touch or a click sound when the switch is shifted from the first OFF state to the ON state. Hence, it is difficult for the operator pressing down the push button 703 to determine whether the push-button switch 701 is in the ON state or enabled for data entry.
In view of the foregoing, it is an object of the present invention to provide a push-button switch ensuring the ON/OFF switching thereof despite a failure of one contact during the manipulation of the push-button switch and to provide a teaching pendant employing the same.
It is another object of the present invention to provide a push-button switch adapted to prevent an unintentional shifting from the ON state to the first OFF state as a result of a slight easing of the depression of the push button and to provide a teaching pendant employing the same.
In accordance with the present invention for achieving the above objects, a push-button switch comprises a switch case; a push button depressibly supported by the switch case; a contact comprising a movable terminal disposed in the switch case in a manner that a first end thereof is rotatable about a second end thereof, and a normally open stationary terminal fixed to place in the switch case and arranged to be in or out of contact with the movable terminal through the rotation of the first end of the movable terminal; an operative member disposed in the switch case in a manner that a first end thereof is rotatable as interlocked with the depression of the push button; urging means having its opposite ends locked to the first end of the movable terminal and the first end of the operative member for urging the first end of the movable terminal while urging the first end of the operative member in a first direction; and releasing means brought into action by more than a predetermined amount of depression of the push button to release the operative member from the interlocked relation with the push button, and is characterized in that when in conjunction with the increase of the amount of depression of the push button, the amount of rotation of the first end of the operative member against the urging means is increased to a first dead point at which the urging force applied by the urging means to the movable terminal is changed from the first direction to a second direction, the movable terminal is brought into contact with the normally open stationary terminal thereby shifting the contact from a first OFF state to an ON state, that when the amount of rotation of the first end of the operative member released from the rotation against the urging means reaches a second dead point at which the urging force applied by the urging means to the movable terminal is changed from the second direction to the first direction, the movable terminal is moved away from the normally open stationary terminal thereby shifting the contact from the ON state to a second OFF state, and that two or more of the contacts are disposed in the switch case and are simultaneously turned ON or OFF by depressing the push button.
According to such an arrangement wherein two or more contacts for switching the push-button switch between the ON and OFF states are disposed in the switch case, the contacts can simultaneously be turned ON or OFF by depressing a single push button. Therefore, in the case of a failure of one of the contacts, for example, the push-button switch can be switched between the ON and OFF states by means of the other contacts. Thus, the push-button switch is improved in reliability.
The push-button switch according to the present invention is characterized in that as to transition from the ON state to the first OFF state resulting from eased depression of the push button, the amount of rotation of the first end of the operative member to reach the second dead point is set smaller than that of rotation of the first end of the operative member to reach the first dead point.
According to this arrangement wherein the amount of rotation of the first end of the operative member to reach the second dead point is set smaller than that of rotation of the first end thereof to reach the first dead point, the movable terminals are separated from the normally open stationary terminals by a smaller amount of depression of the push button than that required for bringing the movable terminals into contact with the normally open stationary terminals.
That is, the push-button switch has a so-called hysteresis characteristic that the switch requires a different amount of rotation of the first end of the operative member to be shifted from the first OFF state to the ON state than that required to be shifted from the ON state to the first OFF state. Therefore, even if the depression of the push button for maintaining the push-button switch in the ON state is eased, for example, the movable terminals are not separated from the normally open stationary terminals so long as the decrease of the depression of the push button is within a predetermined range or unless the amount of rotation of the operative member reaches the second dead point. Thus, the push-button switch is prevented from being inadvertently shifted from the ON state to the first OFF state.
The push-button switch according to the present invention is characterized in that one of the contacts includes a normally close stationary terminal, and that the one contact maintains the movable terminal and the normally close stationary terminal thereof in contacted relation when the other contacts are in the first OFF state, maintaining the movable terminal and the normally close stationary terminal thereof in separated relation when the other contacts are in the ON state, maintaining the movable terminal and the normally close stationary terminal thereof in contacted relation when the other contacts are in the second OFF state.
According to this arrangement wherein the one contact assumes the opposite open/close position to that assumed by the other contacts when the push-button switch is shifted from the first OFF state to the ON state or from the ON state to the second OFF state, it is readily determined that any one of the contacts is in failure when the one contact and the other contacts assume the open or close position at a time.
The push-button switch according to the present invention is characterized in that an auxiliary contact is disposed in the switch case, the auxiliary contact designed to be opened or closed when the contacts are in the first OFF state and to be closed or opened when the contacts are in the second OFF state.
According to this arrangement wherein there is provided the auxiliary contact switched between the open and close positions depending upon the first OFF state and the second OFF state, whether the push-button switch is in the first OFF state or in the second OFF state can be determined by monitoring the open/close position of the auxiliary contact.
More specifically, the movable terminals and the normally open stationary terminals of the contacts are open when the push-button switch is in the first OFF state and when the push-button switch is in the second OFF state. Therefore, it is impossible to determine the push-button switch to be in the first OFF state or in the second OFF state by merely monitoring the open/close relation between the movable terminals and the normally open stationary terminals. However, the provision of such an auxiliary contact permits the determination as to whether the push-button switch is in the first OFF state or in the second OFF state.
The push-button switch according to the present invention is characterized in that the auxiliary contact is provided in correspondence to each of the contacts. According to this arrangement wherein the auxiliary contact is provided in correspondence to each of the contacts, each of the contacts can be determined to be in the first OFF state or in the second OFF state by monitoring the corresponding auxiliary contact.
The push-button switch according to the present invention is characterized in that the auxiliary contact comprises a normally close contact designed to be closed when the contacts are in the first OFF state and to be opened when the contacts are in the second OFF state, and is provided with forcible separation means for forcibly opening the auxiliary contact in the second OFF state.
According to this arrangement, in a case where the auxiliary contact is fused, for example, the forcible separation means can forcibly open the auxiliary contact. This provides a positive distinction between the first OFF state and the second OFF state of the push-button switch.
The push-button switch according to the present invention further comprises a distribution member for evenly distributing a pressing load applied by depressing the push button. According to this arrangement, whatever portion of the push button is depressed, the distribution member evenly distributes the pressing load. This ensures that the plural contacts are opened or closed at a time.
The push-button switch according to the present invention further comprises a rubber cover mounted to place in a manner to cover the push button. According to this arrangement wherein the push button is covered by the rubber cover, the push-button switch is enhanced in watertightness.
The push-button switch according to the present invention further comprises an external button mounted to place in a manner to cover the push button. According to this arrangement wherein the push button is covered by the external button, a top surface of the push button is protected against deformation or fracture.
In accordance with the present invention, a teaching pendant is characterized in that a pendant body includes a left-hand and a right-hand operation sections to be held in the left hand and the right hand, respectively, and the push-button switches disposed at the respective inner sides of the operation sections to be operated by gripping the corresponding operation sections, and that gripping either one of the operation sections shifts the corresponding push-button switch to the ON state thereby enabling a data input operation.
According to this arrangement wherein there are provided the left-hand and right-hand operation sections with the respective push-button switches to be operated by gripping the corresponding operation sections, the data input operation can be done by either hand. In a case where, for example, the left hand is fatigued while depressing the left-hand operation section in order to maintain the push-button switch in the ON state for data input operation, the pendant body may be held by the right hand, in turn, so that the push-button switch may be maintained in the ON state via the right-hand operation section.
The teaching pendant according to the present invention is characterized in that when either one of the operation sections is gripped to shift the corresponding push-button switch at the inner side thereof to the second OFF state, the gripping of the other operation section does not enable the operation of the corresponding push-button switch at the inner side thereof.
According to this arrangement wherein with either one of the push-button switches placed in the second OFF state, the other push-button switch is disabled for operation, an effort to shift the other push-button switch to the ON state, for example, is ineffective to place the teaching pendant in the teaching mode. Thus, the data input operation is inhibited.
In accordance with the present invention, a teaching pendant is characterized in that a pendant body is provided with one piece of the push-button switch and a right-hand and a left-hand manipulation levers to be gripped by the right hand and left hand, respectively, for operative depression of the push-button switch, and that either one of the manipulation levers is manipulated to shift the push-button switch to the ON state, thereby enabling a data input operation.
According to this arrangement wherein the left-hand and right-hand manipulation levers are provided and the push-button switch can be operated via either of the manipulation levers, even when the left hand involved in the operation is fatigued, for example, the pendant body may be held in the right hand so as to continue the data input operation. Furthermore, the teaching pendant is reduced in costs because only one push-button switch is provided in the pendant body.
The teaching pendant according to the present invention is characterized in that when either one of the manipulation levers is gripped to shift the push-button switch to the second OFF state, the gripping of the other manipulation lever does not enable the operation of the push-button switch.
According to this arrangement, when the push-button switch is shifted to the second OFF state by gripping either one of the manipulation levers, the other manipulation lever is disabled for operation. Hence, data cannot be inputted unless both of the manipulation m levers are manipulated to shift the push-button switch to the first OFF state.